THE AUTO SCANNER: The mystery of the check engine light

Monday

Jun 12, 2017 at 6:00 PM

Your car care questions answered by repair expert Larry Rubenstein.

By Larry Rubensteinscanauto@aol.com

Q: I have heard your show on WBZ radio several times now and have always been impressed with the answers you have given callers regarding problems with their automobiles. Consequently, you are my last hope to resolve my problem with my check engine light.

The vehicle in question is a 2010 Cadillac CTS Sports Sedan with the 3.6-liter DOHC V-6 with the six-speed automatic transmission. I bought the vehicle new on June 30, 2010. The vehicle currently has approximately 130,000 miles on it and other than the check engine light has always run perfectly. The vehicle uses no oil between oil changes and has run on Amsoil 5w-30 super synthetic since it had about 5,000 miles on it.

As a former pilot I treat the vehicle like a piece of aviation equipment: It receives great care, is driven gently (the vehicle still has the original Michelin Tires and disc brakes pads and both still have some service life left in them) and literally, the vehicle has been garaged every night.

The codes from the on-board computer keep coming up the same as P-2177 (system too lean, bank 1, off idle) and P-2179 (system too lean, bank 2, off idle). These codes always come up together. My problem is that my “check engine light” is on and has been on for a long period of time now and no one can get it to go off, no matter what is done to the vehicle. This has been going on for a year now. All maintenance items (plugs, coils, filters, etc.) are up to date and the vehicle has been checked extensively for vacuum leaks several times now with none found, yet the problem persists.

The vehicle has been to the dealer many times to address this issue and to private repair garages as well. The vehicle runs so well that on the last 20 highway trips (I live on the Cape and go to Providence a couple of times every week) the vehicle has averaged 28.3 mpg on these trips. On one trip not too long ago, I averaged 30.1 for the entire trip, so obviously the vehicle runs well. If you call on the engine for power, it is literally a rocket ship.

However, I have noticed during the cold weather that when the engine is started it runs smoothly for the first 10 seconds, then there is some very slight unevenness for about 15-20 seconds and then it runs very smoothly thereafter, particularly when the engine is warm. In fact, sometimes when you are in the car stopped at a light, you can’t tell the engine is running.

Is there any advice you can give me? Any help you can give me would be greatly appreciated. Thanks very much for all your anticipated assistance. -- Sincerely, John Hutton

A: Most common issue with this car with this problem is a leaking air intake tube between the MAF (mass airflow) sensor and the throttle body. When stepping on the gas the engine tilt is most likely enough to open the rip in the tube a little bit wider. Getting the air into the engine after the MAF sensor will give you these codes. If the check engine light will not turn off, then your problem is either in the computer or the instrument panel.

Q: My friend has a 2000 VW Passat with 154,002 miles. She took it to a dealer and needs $1,300 in work, and she is quite confused about it. What do you think is it worth sinking that money into it? -- Russ

A: This is a difficult question to answer sight unseen. So let’s start with the body. Is it rusted and dented? Is the interior clean, not worn, and rip free? How are the tires, brakes, transmission and engine? These are all contributing factors.

The car itself has a value of between $2,000 and $3,500, depending on the condition. So, if the above factors are in good shape, and you don’t want to spend $35,000 for a new car, this would not be a bad investment. You certainly cannot replace the car for $1,300.

Have you taken the car to an independent for a second opinion along with prices? If you do look for a second opinion from an independent repair shop, look for the ASE emblem at or near the door. Also make sure they are using Volkswagen Audi Group (VAG) software to repair your car.

Car Care Tip: When getting into your hot car, keep your window partially open during the first five minutes of driving. This is done to let the gasses from the hot dashboard dissipate.

Submit car questions to scanauto@aol.com. For more tips and seasonal articles, visit Rte. 1 Auto Service's Facebook page at facebook.com/Rte-1-Auto-Service, or the shop's website at rte1autoservice.com. You can hear Larry and his son Scott on WBZ's NightSide.

Community Info

Original content available for non-commercial use under a Creative Commons license, except where noted.
Wicked Local Plympton ~ 182 Standish Avenue, Plymouth, MA 02360 ~ Privacy Policy ~ Terms Of Service